Objective: To assess whether non-elective caesarean section due to obstructed labour and/or ineffective uterine contractility was associated with maternal body mass index (BMI).
Study design: The prospective dataset from the Swedish Medical Birth Registry consisted of 233,887 nulliparous women with a spontaneous onset of labour categorized in six classes of pre-pregnancy BMI, who delivered in Sweden between, January 1, 1999 and December 31, 2005. The mode of delivery was classified as either vaginal or by caesarean section. The caesarean section was classified as either elective or non-elective. Adjusted risks for non-elective caesarean section due to ineffective uterine contractility, or obstructed labour or fetal distress were determined using Mantel-Haenszel technique.
Results: The risk of a non-elective caesarean section due to obstructed labour was not significantly associated with maternal BMI. However, ineffective uterine contractility was significantly associated with maternal BMI and the risk of non-elective caesarean delivery due to labour arrest disorders increased with increasing BMI, reaching a 4-fold increased risk among the morbidly obese women. The risk of non-elective caesarean section due to fetal distress also increased significantly with increasing maternal BMI.
Conclusions: It appears that ineffective labour could be a factor leading to the increased risk of non-elective caesarean section among obese and morbidly obese women. These findings challenge obstetricians to learn more about how to manage oxytocin infusions during labour in relation to maternal BMI.